This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cognitive deficits and academic failure are common problems encountered by the clinician caring for children with NF1. To fully understand the natural history of NF1, it is essential to assess cognitive development from infancy throughout childhood. The purpose of this study is to characterize the neurocognitive development of children with NF1 from 5 months to 7 years of age through neuropsychological/developmental assessment to identify early predictors of cognitive outcome in young children with NF1. We will also document the onset and natural history of MRI-T2 hyperintensities on MRI scan. This will allow us to evaluate the relationship between neurodevelopmental parameters in young children with NF1 and the location, size, and intensity of T2 hyperintensities on MRI scan. We hypothesize that young children with NF1 will demonstrate greater cognitive and motor delays than the control population. We further hypothesize that the presence and location of T2 hyperintensities will correlate with cognitive dysfunction, and development delays detected in young children wll be predictive of later cognitive problems.